I have macbook pro 1211 & A1286 -- I need power adapter to work w/ both--I got with new mac= 60 watt, old 1 was 85 w-- why?

The 2 macbook pros have different model numbers: A1211 and A1286. the new one has 60 watt adapter -- how different is it from the adapter needed for the A1211? Origin equip for old machine was 85w...what do i look for to work with both?